1. Field of the Invention
This invention relates to transversal filters employing charge transfer technology, and more particularly, to a programmable or adaptable charge transfer device transversal filter having a floating electrode under each sensing electrode for controlling the associated depletion capacitance in order to introduce weighting factors.
2. Description of the Prior Art
A transversal filter convolves an incoming signal with the impulse response of the filter. The convolution can be performed by applying the incoming signal to the input of a charge transfer device analog shift register and forming a weighted summation of the charge at each stage of the register. Ordinarily, the signals at each stage of the shift register are tapped or sampled, multiplied by "weighting factors" and then added or summed.
Transversal filters having adjustable weighting factors are known. Charge transfer device transversal filters with adjustable weighting factors are also known, but the charge signal is first sensed and then weighted as a separate circuit function external to the charge transfer cell. Charge transfer device transversal filters which have weighting factors associated with the charge sensing are also known but the weighting factors are not programmable or electronically adjustable. U.S. Pat. No. 3,819,958 is exemplary of such nonprogrammable charge transfer transversal filters. Each is characterized by split transfer electrodes which introduce invariable weighting factors determined by relative areas of the resulting electrode portions. No known charge transfer transversal filter employs floating electrodes under the sensing electrodes to bias depletion regions in order to control depletion capacitances for a weighting purpose or for any other purpose.